Three-phase four-wire hybrid power filter using a smaller power converter

Abstract In this paper, a hybrid power filter is proposed to solve problems of line harmonic currents and neutral line currents of three-phase four-wire power distribution system. This hybrid power filter is configured by a there-phase tuned power filter and a three-phase power converter. The tuned power filter is configured by a capacitor and an inductor, and its tuned frequency is setting at the frequency of third-order harmonics. The three-phase power converter has a four legs bridge structure and is connected to the inductor of the tuned power filter in parallel. The three-phase power converter is applied to solve the problems of series/parallel resonance and improve poor filter performance. Furthermore, it also forces the fundamental current of the tuned power filter and the dominant harmonic current of the nonlinear load to flow through the inductor of the tuned power filter. In this way, the voltage rating of the three-phase power converter is reduced because it is serially connected to the power capacitor of the tuned power filter, and the current rating can be diminished because it is connected to the inductor of the tuned power filter in parallel. Hence, the power rating of the power converter applied in the proposed hybrid power filter is minimized. A DSP based prototype is developed and tested to verify the performance of the proposed three-phase four-wire hybrid power filter. Experimental results show that the proposed three-phase four-wire hybrid power filter achieves the expected performance.